The present invention relates to a valve stem seal assemblies for use in internal combustion engines and in particular to sealing media retainers for such seal assemblies.
Those skilled in the art will appreciate the manner in which intake and exhaust valves are employed in cylinder heads of internal combustion engines. Such valves, supported for reciprocal motion within valve guides, include integral elongated valve stems extending away from the engine cylinder heads. The ends of the valve stems interact with rotating cams for cyclic repeated opening and closing of the valves against the force of valve return springs during a combustion cycle. Obviously, in order to permit unobstructed reciprocal movement of the valve stem in the valve guide, some mechanical clearance must exist between the valve guide and the moving valve stem. The valve stems thus move reciprocally to and from the cylinder head, each within its individual valve guide, and so-called valve stem seal assemblies are used to seal against leakage of oil through a clearance path between each annular engine valve guide and its associated valve stem.
Thus, as is well known, the intake port of a combustion chamber is opened and closed by the reciprocating motion of at least one intake valve, which in turn is driven by the rotary motion of a cam, the latter being affixed to and rotatable with an engine camshaft. The intake valve permits fuel mixed with air to flow into the combustion chamber. In addition, an internal combustion engine has at least one exhaust valve and associated exhaust port for releasing expended combustion gases to the atmosphere. Typically, intake and exhaust valves are of similar construction and both include valve stems integrally affixed to the valves.
In the typical engine, a valve stem seal assembly is fitted over or atop each valve guide, wherein each assembly has a retainer frictionally mounted to an associated valve guide, or is retained in place via cooperation of a return spring and a retainer flange, to assure attachment of the valve stem seal assembly within the engine. Typically each valve stem seal assembly has two primary parts; 1) an elastomeric oil seal positioned at one end to control leakage of oil between the valve stem and the valve guide, and 2) a structural cylindrical part called a retainer mounted atop of the valve guide. In many cases, the retainer has a so-called bottom flange that extends circumferentially about the bottom of the valve guide for supporting the retainer on the cylinder head deck. Additionally, traditionally manufactured elastomeric oil seals include an exterior groove for receiving a xe2x80x9cgarter springxe2x80x9d as described below.
Much progress has been achieved in the art of valve stem seal assembly design and construction. However, several design issues remain problematic for traditional valve stem seal assemblies. For example, the number of parts associated with a valve stem seal assembly has typically been the seal body and the retainer. However, a third part, called a xe2x80x9cgarter springxe2x80x9d is often disposed within a circumferential groove about the exterior of the seal body to impart a hoop stress or force to engage the seal body with the valve stem and prevent leakage of oil. The garter spring is typically made of metal and adds additional cost to the seal body assembly. An additional difficulty with traditional seal assemblies is verification of proper installation. Use of the garter spring with the retainer requires separate verification for each part. This additional verification also adds to the cost of the seal body assembly.
The inventors of the present invention have recognized these and other problems associated with traditional valve stem seal assemblies. To this end, the inventors have developed an improved valve stem seal assembly that eliminates the need for an additional garter spring while still securing a seal body to a top of a valve guide and engaging a valve stem.
Specifically, the invention is a valve stem seal assembly adapted for installation atop a valve guide of an internal combustion engine for sealingly engaging a valve stem reciprocally moveable through the valve guide. The valve stem seal assembly comprises a resilient annular seal body defining an interior annular sealing lip adapted to engage the valve stem and further including first and second exterior annular grooves. The assembly also comprises a retainer defining a generally rigid cylindrical body with upper and lower body ends and further defining an axis. Furthermore, the assembly includes a first set of fingers disposed from the lower body end to the upper body end of the retainer. The first set of fingers comprises radially inwardly depending upper ends at the upper body end of the retainer for engaging the first exterior annular groove of the seal body to maintain the seal body axially against the top surface of the valve guide. Additionally, a second set of fingers is disposed between the lower body end and the upper body end of the retainer. The second set of finger comprises radially inwardly depending upper ends for engaging the second exterior annular groove of the seal body to impart a circumferential force urging the sealing lip against of the reciprocally moveable valve stem.